1. Field of Invention
The present invention generally relates to the field of lighting devices, and more particularly, to a system and method of controlling lighting fixtures for coordinating precise brightness and color schedules so as to closely resemble sunlight on a cloudless day in spectral characteristics.
2. Description of Related Art
With growing demand for energy efficient lighting, new lighting technologies such as LEDs offer distinct opportunities due to their customizable colors and precision in control. As the white LED lighting market grows, advancing the state of the art entails a seamless integration of artificial light with natural light and healthful lighting through dynamic lighting.
One particular niche of such LED design and control is in the generation of artificial sunlight for variety of reasons, especially for treating human ailments, e.g., circadian rhythm disorders, seasonal affection disorders, shift work conditions, etc.
U.S. Pat. No. 6,350,275 (Vreman et al.) relates to a pair of personal glasses with built in LED's within 3 cm of the eye which directs red and blue light into the user's eyes to treat circadian rhythm disorders. However, this invention is limited to one user, must be worn during the working period and does not simulate natural sunlight.
The following patents propose similar methods of treating circadian rhythm disorders, but wherein they do not replicate natural sunlight conditions, involve a portable or wearable device, involve treatment periods which are intermittent and require that the patient engage with the device, or involve chromatic properties of treatment light which are not defined: U.S. Pat. Nos. 5,503,637 (Kyricos, et al.); 6,053,936 (Koyama, et al.); 5,197,941(Whitaker); 5,545,192 (Czeisler, et al.); 5,176,133 (Czeisler, et al.); and 5,304,212 (Czeisler, et al.).
Examples of other lighting control systems are mentioned below:
U.S. Pat. No. 7,014,336 (Ducharme, et al.) relates to active circuitry with a feedback mechanism for reading the light in the room and actively adjusts. In particular, the invention relates specifically to color temperature variable lighting fixtures but without relating a specific region of the blackbody curve or chromaticity diagram. It also does not appear to teach or suggest a method for automatically adjusting the color temperature and brightness of the lighting fixtures without user input.
U.S. Pat. No. 7,213,940 (Van De Ven et al.) involves reducing light with specific coordinates (dimming and feedback) utilizing different families of LED emitters and adjusts for specific output at constant color temperature at a sacrifice of brightness. This patent is also static embedded systems with controls within the fixture. This invention relates to a variable color temperature adjustable over time with active controls. In particular, the invention involves a specific 5-sided bounding box on the CIE (Commission Internationale de l'Eclairage) 1931 chromaticity diagram. It specifies that a first group of lighting elements must have chromaticity coordinates at a first point (defined) and a second group must have coordinates falling within the defined box. Additionally, this patent relates to a lighting fixture producing a fixed color temperature.
U.S. Pat. No. 7,354,172 (Chemel, et al.) relates to rendering lighting conditions based on a reference color gamut common to many lighting units in a network using white and monochromatic LEDs. This patent does not specifically define the color gamut or the colors or chromaticity coordinates the fixture operates at, and does not appear to teach or suggest a means by which brightness and color are autonomously and dynamically changed with time.
U.S. Pat. No. 6,459,919 (Lys, et al.) discloses illumination of living tissues where known light parameters relate to a condition of the living tissue. This is discussed in the context of using light to identify abnormal features and pathological conditions of tissues, living matter, and other materials. The therapeutic applications mentioned in the background extend only to diagnostic methods, and do not appear to teach or suggest using lighting conditions to stimulate a biological response.
U.S. Pat. No. 6,441,558 (Muthu, et al.) relates to a fixture employing red, green, and blue LEDs and a control mechanism such that the fixture outputs a constant color temperature and brightness.
U.S. Pat. No. 6,340,868 (Lys, et al.) relates to lighting units on a network capable of receiving addressing commands and controls for controlling a plurality of LEDs in each unit. However, this invention does not deal with methods by which lighting conditions are changed (i.e. color schedules), specific chromatic regions the fixtures recreate, or methods to ensure color consistency (i.e. feedback loops or sensors).
U.S. Pat. No. 7,173,384 (Plotz, et al.) relates to recreating a predetermined region on a CIE chromaticity diagram using pulse width channels of red, green, and blue LEDs arranged in channels of up to six.
U.S. Pat. No. 7,067,995 (Gunter, et al.) discloses the use of a temperature sensor and calibrations, along with sensor calibration data storage at various reference temperatures as a means of correcting color fluctuations related to the thermal state of the LEDs.
U.S. Pat. No. 6,992,803 (Chang) relates to a feedback mechanism which calculates the chromaticity coordinates of each lighting element in a lighting fixture to calculate the proper operating conditions necessary to reproduce a specific chromaticity coordinate.
U.S. Pat. No. 6,683,419 (Kriparos) discloses a method by which LEDs, with linear dimming—brightness curves, mimic incandescent bulbs, which have exponential dimming—brightness curves. The invention involves the dimming-brightness relationship in an LED fixture and does not appear to teach or suggest changing color with dimming level.
U.S. Pat. No. 7,327,337 (Callahan) involves a series of lighting devices connected to a two wire power bus in which the color modulation signals are transmitted through the power connection and demodulated in the lighting device.
U.S. Pat. No. 6,806,659 (Mueller, et al.) covers a lighting control network for LED luminaires as well as various LED lighting fixtures for several applications. See also U.S. Patent Publication No. 20040178751(Mueller, et al.).
U.S. Pat. No. 4,962,687 (Belliveau, et al.) deals with variable colors in a lighting system achieved by dimming circuitry within fixtures. It does not appear to cover specific chromatic regions rendered using a control feedback loop.
U.S. Pat. No. 5,350,977 (Hamamoto, et al.) involves a variable color temperature fixture, and does not incorporate a means of autonomously and dynamically changing the color temperature and or brightness with respect to the time of day or geographic location.
U.S. Pat. No. 5,357,170 (Luchaco, et al.) claims a control system where preset conditions can be changed by the occupant by moving a physical member or slider control to change the maximum brightness levels of the system. This patent does not appear to address color modulation over time or lighting schedules or programs.
U.S. Pat. No. 7,288,902 (Melanson) deals first with a lighting fixture with two unique lighting elements, each possessing a fixed color temperature, which are then dimmed at different ratios relative to the AC power dimming level to achieve a variable color temperature with dimming level. This patent claims only “white” and “yellow” LEDs, and does not appear to teach or suggest the ratios or specific chromatic region rendered by the lighting device. This patent also does not appear to teach or suggest any method by which a control system can interface with a fixture, or any method by which the brightness and color temperature of the fixture can be controlled independently.
U.S. Pat. No. 6,720,745 (Lys, et al.) discloses the use of the RS-485 standard to control a plurality of LED devices.
U.S. Pat. No. 7,215,086 (Maxik), issued relates to integrating the fixture designs within the Lutron Circuits to achieve diming levels below 5% through pulse modulation. This invention utilizes a square wave which has been discussed in prior art.
U.S. Pat. No. 5,193,900 (Yano, et al.) discloses a device which detects natural light and mechanically actuates a filter on an artificial light source.
U.S. Pat. No. 6,554,439 (Telcher, et al.) teaches a method of treating circadian rhythm disorders using light sources and a rotating filter.
U.S. Pat. No. 7,446,303 (Maniam, et al.) discloses an ambient light sensor suitable for determining lighting conditions, but does not practice a lighting device or a system of lighting devices.
U.S. Pat. Nos. 7,387,405 and 7,520,634 (Ducharme, et al.) pertain to a system of lighting devices capable of producing a broad range of lighting conditions, however they do not utilize a specific collection of at least three lighting elements of a characteristic chromaticity (as is disclosed in the present application, as will be discussed later), and do not teach a method by which the user can prescribe a particular flux of blue light within white light.
U.S. Pat. No. 7,319,298 (Jungwirth, et al.) relates to a luminaire system which produces light of a desired chromaticity and luminous flux output with varying ambient temperature. The prior art teaches a method by which the luminaire regulates chromaticity throughout changing temperatures using sensors.
U.S. Pat. No. 5,721,471 (Begemann, et al.) discloses a lighting system which manipulates artificial lighting based on actual lighting conditions, determined either by a light sensor exposed to natural light or by the calendar day and time of day. It also discusses modification to artificial lighting conditions based on a modification to present mean day-lighting levels. In contrast (as will be discussed in detail later), the present invention relates a desired result or circadian response to the generation of signals to control lighting devices and the ultimate generation of artificial light. This method of input is based on user preference rather than a prescriptive input based on a default time of day or existing lighting conditions for a fixed geographic location. The present invention allows the user to adjust for jet lag after travel, maintain the lighting conditions of a fixed geographic location throughout any location, coordinate the circadian rhythm to a cycle other than 24 hours, or specify a desired circadian response or condition.
U.S. Pat. No. 7,679,281 (Do Hyung, et al.) teaches a lighting device with three lighting elements, two of which comprise an LED chip combined with a phosphor of a specific composition and a third LED chip which emits light in the visible range of 580 nm or more. This third lighting device emitting visible light of 580 nm is described as a lighting element which produces light of 3000K or less, however no specific spectral distributions of light are disclosed. In contrast (and as will be discussed in detail later), the present invention relates to a collection of lighting elements with specific chromaticity characteristics such that the flux of blue light can be precisely controlled through independent modulation of each lighting element while maintaining high color rendering index of the artificial white light. The selection of the lighting elements in the present invention may comprise any collection of lighting elements which produce light in the characteristic chromaticity regions described in FIGS. 13a-14b of the present application. Furthermore, it is within the scope of the present invention that any lighting device of a characteristic chromaticity illustrated in FIGS. 13a-14b of the present application be used to generate artificial light of high color rendering index in the range of 1800-6500K. These lighting devices may be composed of (but are not limited to) LED chips, LEDs combined with phosphors, LED chips combined with quantum dots, LED chips combined with photonic crystals, organic light emitting diodes (OLED), or polymeric LED devices (PLED).
U.S. Patent Publication No. 20030133292 (Mueller, et al.) discloses many applications of color temperature variable lighting. Daylight simulation and circadian rhythm disorder treatment is not mentioned.
U.S. Patent Publication No. 20030100837 (Lys, et al.) relates to therapeutic effects achieved with LED devices; it claims: an LED system for generating a range of colors within a color spectrum, selecting from the range of colors a set of colors, whereby the set of colors produces in the patient a therapeutic effect, and illuminating an area of the patient with the set of colors for a period of time predetermined to be effective in producing the therapeutic effect. The patent does not appear to identify the range of colors which produce the therapeutic effect, nor does it appear to identify a period of time or method of modulation of the light to facilitate this therapeutic effect.
See also the following U.S. patent publications regarding LED lighting controls: U.S. Patent Publication Nos. 20050253533 (Lys, et al.); 20050236998 (Mueller, et al.); 20050231133 (Lys); 20050218870 (Lys); 20050213353 (Lys); 20050200578 (Lee, et al.); 20050151489 (Lys); 20040212321(Lys, et al.); and 20040105264 (Spero).
However, despite the foregoing, there remains a need for a system and method that generates broad spectrum white light of color temperatures 1800K to 6500K in interior spaces using general lighting fixtures (e.g., for treating circadian rhythm disorders) and wherein brightness and color are autonomously and dynamically changed with time and while using combinations of white LEDs and color LEDs. Furthermore, there remains a need for such a system and method that does not require calculating chromaticity coordinates but rather uses calibration values of sensor outputs at specific color temperatures and preferably, for controlling a feedback loop, and a color matching algorithm.